Embodiments relate to a transmission and reception signal detecting system applied to an antenna circuit of a mobile communication terminal, and more particularly, to transmission and reception signal detecting apparatus and method for checking performance of the antenna circuit.
Mobile communication terminals include a radio frequency (RF) circuit for wireless communications, to transmit and receive an audio signal and a data signal through an antenna.
In particular, antennas, which are main parts for transmitting and receiving a signal and largely affect a call quality, are designed to satisfy a maximum transmission condition (50Ω matching), thereby optimally transmitting and receiving data. In addition, active research has been carried out on antennas having improved reception sensitivity to ensure transmission and reception performance.
The performance of an antenna may be evaluated using a voltage standing-wave ratio (VSWR). The VSWR is a voltage ratio measured at an adjacent node and an antinode in a waveguide or transmission line having a standing wave, or a ratio of a maximum standing wave amplitude to the minimum standing wave value. For example, a wave travelling in two media having two different impedances is divided into a forward wave and a reflected wave due to an impedance mismatch, and difference between the forward wave and the reflected wave causes the VSWR.
That is, if the VSWR is equal to 1, a line impedance completely matches with a terminal impedance, and an incident wave reaches a destination end without reflection. As the VSWR increases over 1, the amount of reflection increases. Thus, the VSWR is a main index for detecting a defect of an antenna.
Recently, research has been continually carried out on a transmission and reception signal detection system capable of more accurately measuring the VSWR to detect a defect of an antenna.